1. Field of the Invention
This invention relates to a washable air filter for an internal combustion engine used for removing dust particles from air to be supplied to an internal combustion engine.
2. Description of the Prior Art
Generally, an internal combustion engine such as an engine for an automobile or the like requires enormous amount of air. If the air supplied to the Internal combustion engine contains dust particles, there is a case that cylinders in the internal combustion engine are damaged, so that the dust particles are removed by using an air filter.
Various shapes of air filters are used according to types or displacements of engines. In recent years, a cylindrical air filter 1A shown in FIG. 7 has been mainly used for engines of automobiles, because it is small in size and has high performance.
In the conventional cylindrical air filter 1A shown in FIG. 7, a filter element 40 having a substantially cylindrical configuration is used. The filter element 40 is formed from a cylindrically formed pleated-sheet in that peaks 41 and valleys 42 are arranged alternately. By using such a filter element 40, it becomes possible to provide a high-performance air filter 1A which is small in size and has large surface area.
In the conventional air filter 1A, the filter element 40 is formed from a sheet material such as non-woven cloth, paper, glass fiber or the like. In such sheet materials, fibers are tangled with each other so that fine or very small openings are complicatedly and irregularly formed among the fibers. During filtration, when air taken from the atmosphere passes through the openings, dust particles contained in the air are trapped by the complicatedly tangled fibers. In this way, the dust particles are removed from the air.
As described above, since the filter element removes dust particles from air by trapping them with the complicatedly tangled fibers, the dust particles are gradually deposited within the filter element due to filtration, and as a result, the filter element will be eventually clogged. In particular, since working vehicles such as concrete mixer vehicles and the like are operated in construction sites where a cloud of dust is generated, air filters used for such working vehicles are likely to be clogged.
When the filter element is clogged, it becomes difficult that air passes through the filter element, which causes insufficient air supply to the engine, resulting in incomplete combustion of the engine. Also, this causes poor fuel consumption and environmental problems such as increase in environmental pollutants contained in exhaust gas or the like.
Therefore, the filter element must be replaced before it is clogged.
As described above, in the conventional air filter 1A, non-woven cloth, paper, glass fiber or the like is used as a material for the filter element 40, and such materials have a structure in that fibers thereof are complicatedly tangled with each other. Because of such structure, the dust particles trapped by the filter element remain inside thereof.
Therefore, even if high-pressure air or the like blows on the filter element for cleaning, it is not possible to remove the dust particles trapped by the complicatedly tangled fibers from the filter element 40. Further, if the filter element of the conventional air filter 1A is washed with water, there is a case that the material of the filter element is deteriorated, especially when the filter element is formed from a paper material.
For these reasons, the conventional air filter using such filter element described above can not be reused. Most of the air filters are disposed of by incineration or the like after their use. However, since the filter elements use organochlorine based adhesives or the like as an adhesive, toxic substances such as dioxin and the like are generated when such filter elements are incinerated, thereby causing an environmental problem.